Poly(isobutylene-co-isoprene), or IIR, is a synthetic elastomer commonly known as butyl rubber which has been prepared since the 1940's through the random cationic copolymerization of isobutylene with small amounts of isoprene (1-2 mole %). As a result of its molecular structure, IIR possesses superior air impermeability, a high loss modulus, oxidative stability and extended fatigue resistance.
Butyl rubber is understood to be a copolymer of an isoolefin and one or more, preferably conjugated, multiolefins as co-monomers. Commercial butyl comprises a major portion of isoolefin and a minor amount, not more than 2.5 mol %, of a conjugated multiolefin. Butyl rubber or butyl polymer is generally prepared in a slurry process using methyl chloride as a diluent and a Friedel-Crafts catalyst as part of the polymerization initiator. This process is further described in U.S. Pat. No. 2,356,128 and Ullmann's Encyclopedia of Industrial Chemistry, volume A 23, 1993, pages 288-295.
Halogenation of this butyl rubber produces reactive allylic halide functionality within the elastomer. Conventional butyl rubber halogenation processes are described in, for example, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A231 Editors Elvers, et al.) and/or “Rubber Technology” (Third Edition) by Maurice Morton, Chapter 10 (Van Nostrand Reinhold Company© 1987), particularly pp. 297-300.
The presence of allylic halide functionalities allows for nucleophilic alkylation reactions. It has been recently shown that treatment of brominated butyl rubber (BIIR) with nitrogen and/or phosphorus based nucleophiles, in the solid state, leads to the generation of IIR-based ionomers with interesting physical and chemical properties (see: Parent, J. S.; Liskova, A.; Whitney, R. A; Resendes, R. Journal of Polymer Science, Part A: Polymer Chemistry 43, 5671-5679, 2005; Parent, J. S.; Liskova, A.; Resendes, R. Polymer 45, 8091-8096, 2004; Parent, J. S.; Penciu, A.; Guillen-Castellanos, S. A.; Liskova, A.; Whitney, R. A. Macromolecules 37, 7477-7483, 2004). The ionomer functionality is generated from the reaction of a nitrogen or phosphorous based nucleophile and the allylic halide sites in the BIIR to produce an ammonium or phosphonium ionic group respectively. The physical properties of these BIIR based ionomers (green strength, modulus, filler interactions etc.) are superior to those of their non-ionomeric counterpart.
It has been previously discovered that the addition of para-methylstyrene to the mixed feed of butyl polymerizations (MeCl, IB and IP mixed feed, with AlCl3/H2O as initiator) results in a high molecular weight polymer with up to 10 mol % of styrenic groups randomly incorporated along the polymer chain (Kaszas, U.S. Pat. No. 6,960,632; Kaszas et al. Rubber Chemistry and Technology, 2001, 75, 155). The incorporation of para-methylstyrene is found to be uniform throughout the molecular weight distribution due to the similarity in reactivity with isobutylene. The isoprene moieties within the butyl terpolymers can be halogenated by conventional methods leading to similar Type II and Type III allylic halide structures as the current LANXESS halobutyl grades.
CA 2,418,884 and 2,458,741 describe the preparation of butyl-based, peroxide-curable compounds which have high multiolefin content. Specifically, CA 2,418,884 describes the continuous preparation of IIR with isoprene levels ranging from 3 to 8 mol %. Halogenation of this high multiolefin butyl rubber produces a reactive allylic halide functionality within the elastomer. With these elevated levels of isoprene now available, it is possible, in principle, to generate BIIR analogues which contain allylic bromide functionalities ranging from 3 to 8 mol %. Conventional butyl rubber halogenation processes are described in, for example, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A231 Editors Elvers, et al.) and/or “Rubber Technology” (Third Edition) by Maurice Morton, Chapter 10 (Van Nostrand Reinhold Company © 1987), particularly pp. 297-300.
Alternatively, a butyl copolymer may comprise a C4-C7 isomonoolefin, such as isobutylene, and a comonomer, such as para-alkylstyrene, preferably para-methylstrene. When halogenated, some of the alkyl substituent groups present in the styrene monomer units contain a benzylic halogen. Additional functional groups can be incorporated by nucleophilic displacement of the benzylic halogen with a variety of nucleophiles as described in U.S. Pat. No. 5,162,445. Use of tertiary amines and phosphines results in the formation of butyl ionomers based on these copolymers with improved physical properties.
There has been continuous effort over the last few decades to develop polymers which inherently possess antibacterial, antifungal and/or antialgal properties by impregnation with an antibacterial, antifungal or antialgal agent. These agents are generally low molecular weight compounds such as antibiotics, phenols, iodine, quaternary ammonium compounds or heavy metals such as silver, tin and mercury. These agents may be attractive, but provide limited protection due to the difficulty in controlling the rate of diffusion of the additive out of the polymer matrix. This leaching eventually renders the material ineffective, possesses a potential environmental risk, and creates the potential for reaction of the leached material with other organic substances. As well, releasing these agents into the environment increases microbial resistance to the agents.
Organic antibacterial, antifungal or antialgal agents have limited incorporability into polymer compositions because, being organic, they typically have a vaporization point less than the temperatures involved during the formation of the polymer compositions. Previous studies have shown that polymeric compounds containing permanently bound antibacterial, antifungal or antialgal agents display advantages over polymeric compounds which contain unbound conventional low molecular weight counterparts. Compounds with conventional agents exhibit better durability with low liberation of toxic products into the environment, thereby reducing losses associated with volatilization, photolytic decomposition, and transportation. Moreover, increased efficiency, selectivity and handling safety are additional benefits that may be realized.
With other polymeric systems in which the antibacterial, antifungal or antialgal agent is bound to the polymer, incorporation of the active material in the polymer is often part of the polymerization process, which can lead to process problems and/or loss of polymer properties. Additionally, the modification of a polymer to incorporate an antibacterial, antifungal or antialgal agent may lead to negative effects on the physical properties of the polymer, rendering the polymer less suitable for its intended application.
Although polymeric compounds containing an antibacterial agent have been prepared and tested, very few examples with adequate antibacterial capabilities have been discovered. In particular, a number of compounds are effective against gram negative bacteria such as Escherichia coil and Salmonella, but few are also effective against gram positive bacteria such as Staphylococcus, Bacillus, Listeria and Streptococcus. 
As such, the present invention is directed to the use of butyl ionomers in reducing a population of and/or preventing accumulation of organisms, and coatings for articles made from the butyl ionomers.